Sorafenib is an oral multikinase inhibitor and among its targets are several RTKs involved in tumor genesis (Raf, Flt-3, c-Kit and RET) and angiogenesis (VEGFR1, 2 and 3 and PDGFRß). Therefore sorafenib inhibits tumor growth by a dual mechanism, acting either directly on the tumor (through inhibition of Raf and Kit signaling) and/or on tumor angiogenesis (through inhibition of VEGFR and PDGFR signaling.